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January 31, 2017

VIDEO: Watch three planets orbit a star 129 light years from Earth

by Chuck Bednar

Images of four distant exoplanets collected over a seven-year span have been combined to create a short video of these massive worlds (all of which are more massive than Jupiter) orbiting a star located some 129 light years from Earth, NASA officials revealed last Wednesday.

This gif was created by researchers at the Nexus for Exoplanet System Science (NExSS), a group sponsored by NASA. When these planets were discovered in 2008, they were some of the first exoplanets to be observed directly. (Image credit: astrobiology.nasa.gov)

The NExSS researchers took seven years worth of observations from Hawaii’s Keck Observatory and combined them into the footage that shows the planets, represented as small white specks, as they orbit HR 8799 (which was blacked out so that its light did not obscure the planets).

None of the orbits depicted in the video are complete, and there’s a very good reason for that: it would take at least 40 years of observations to show any of the planets complete one full journey around their sun, and the furthest one would take 400 years, according to NASA.

“Astronomers have made videos of exoplanets orbiting before, but usually they've done it by blinking frames, so you'd see the planet jump around in its orbit,” Jason Wang, an astronomy student at the University of California-Berkeley who helped created the animation, told Vox.

System may not yet be completely stable, researchers warn

Wang also explained that the four planets depicted in the video appear to be in resonance with each other, meaning that they exert a regular, periodic gravitational influence on one another. In this case, the exoplanets demonstrate a one-two-four-eight resonance, which means that each of them has an orbital period in nearly precise ration with the others in the system.

The pictures featured in the video were initially collected by Dr. Christian Marois of the National Research Council Canada’s Herzberg Institute of Astrophysics, who led the team that discovered three of the four HR 8799 planets using direct imaging in 2008. According to Wang, the video is based on eight observations of the four planets made since 2009.

HR 8799 is believed to be five times brighter than the sun and less than 60 million years old, the researchers said. The four planets orbiting it are believed to be quite far apart, which should be no surprise given their tremendous masses. They move in almost circular motion around the star, Wang noted, and additional research will be needed to determine if the star’s system is stable, or if one or more of these worlds will eventually be ejected into space.

While the first three HR 8799 were officially discovered nine years ago, astronomers later found out that they had actually already been observed by the Hubble Space Telescope. The fourth was discovered following additional observations of the star system in 2009 and 2010. While it orbits inside the other three worlds, it is still 15 times further away from its star than Earth is from the sun.